Electrostatic precipitator

ABSTRACT

AN ELECTROSTATIC PRECIPITATOR FOR COLLECTING DUST, COMPRISING A HORIZONTAL CYLINDRICAL PRESSURE HOUSING HAVING A GAS INLET AT ONE END, A GAS OUTLET AT THE OTHER AND A DUST DISCHARGE OPENING IN THE BOTTOM, PLATE-LIKE COLLECTING ELECTRODES THEREBETWEEN AND DEFINING PARALLEL HORIZONTAL GAS PASSAGES BETWEEN THE INLET AND OUTLET, AND CHARGING ELECTRODES BETWEEN THE COLLECTING ELECTRODES, AND MEANS FOR REMOVING THE COLLECTED DUST FROM THE HOUSING.

Sept. 28, 1971 J. M R ETAL 3,608,275

ELECTROSTATIC PRECIPITATOR Filed NOV. 20, 1969 5 Sheets-Sheet 1 EN WIEHER Muss-( e B Z Y kR M in 1 I V w A'TTDRNE s Sept. 28, 1971 w M ETAL ELECTROSTATIC PRECIPITATOR 5 Sheets-Sheet 5 Filed Nov. 20, 1969 R w P55 mM n DE N MI W M Z e N M N A MMM Twtfw VT WA A T Um, g

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ELECTROSTATIC PRECIPITATOR 5 Sheets-Sheet 4.

Filed Nov. 20, 1969 hive/21ers" JEAN WIEMER :FRANKZ. miss 8 m gy m \x ATTORNEYS Sept. 28, 1971 EME Em 3,608,275

ELECTROSTATIC PRECIPITATOR 5 Sheets-Sheet 5 Filed Nov. 20, 1969 lave/Mars:- \TEA N \N I M United States Patent 3,608,275 ELECTROSTATIC PRECIPITATOR Jean Wiemer, Oberhochstadt, and Franz Hauss, Frankfurt, Germany, assignors to Metallgesellschaft Aktiengesellschaft, Frankfurt, Germany Filed Nov. 20, 1969, Ser. No. 878,505 Claims priority, application Germany, Jan. 7, 1969, P 19 526.6 Int. Cl. B03c 3/76 U.S. Cl. 55-112 7 Claims ABSTRACT OF THE DISCLOSURE An electrostatic precipitator for collecting dust, comprising a horizontal cylindrical pressure housing having a gas inlet at one end, a gas outlet at the other and a dust discharge opening in the bottom, plate-like collecting electrodes therebetween and defining parallel horizontal gas passages between the inlet and outlet, and charging electrodes between the collecting electrodes, and means for removing the collected dust from the housing.

PRIOR ART German Pat. 1,162,815 describes a wet electrostatic precipitator for collecting dust in which the electrostatic collecting fields are accommodated in a pressure vessel and Venturi tube afterwashers are accommodated in chambers which are defined by partitions.

Austrian Pat. 189,722 describes a wet electrostatic precipitator for collecting dust which is contained in a pressure container which functions at the same time as a washer and cooler and in which the gas flow is deflected through 180.

These two apparatus known in the art are wet electrostatic precipitators. The electrostatic collecting fields proper, in which the dust is electrostatically collected, do not occupy the entire cross-section of the container but only square or rectangular coaxial portions of the crosssection. As a result, a substantial structural expenditure is required to promote a homogeneous distribution of gas within the electrostatic collecting fields, and shields protecting the high-voltage lead-ins and the dust discharge systems must be provided in the lower and upper portions of the cylindrical container.

When such a dust collector is operated in a dry process, a number of shields are required to avoid a re-entrainment of the collected dust which has been removed from the electrodes. Also, means such as conveyors must be provided to discharge the collected dust. See German Pat. 1,275,457. Because the housing is circular in cross-section, the discharge of dust is particularly difficult as the collected dust settles on the sloping walls throughout the lower semicircle of the cross-sectional configuration.

THIS INVENTION It is an object of the invention to eliminate the disadvantages of the known processes with reasonable structural expenditure, to utilize the spaces which are dead in the known apparatus, to provide a properly acting dust discharge mechanism, and to provide an apparatus which is designed to be operated with air and explosive gases in alternation, special care being taken to avoid any dead spaces in which explosive gas mixtures can form when there is a change of gas or air.

According to this invention, the collecting electrodes in a gas-tight cylindrical housing of an electrostatic precipitator are suspended from horizontal carriers, which extend at the upper portion of the periphery of the housing and parallel to the center line of the housing, and the height of the collecting electrodes corresponds to respective vertical chords of the circular cross-section.

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A plurality of annular carriers are provided in the cylindrical housing and serve to take up the weight of the internal fixtures and to stabilize the housing.

In a preferred embodiment of the invention, a dust discharge opening is provided on the underside of the housing and extends throughout the length thereof.

The dust which is cleaned from the electrodes in the lower portion of the horizontal cylindrical housing is removed by scrapers, which are pivoted on the axis of the housing and extend throughout the length of the dust collector.

The scrapers preferably comprise at least two sets of two arms or struts which extend from a common point on the center line of the housing at an angle of about I 60 to each other. Scoops are pivotedly mounted on the lower outer end of the struts. The pivoted scoops are positively controlled.

The apparatus according to the invention avoids the above-described disadvantages of the prior art and atfords a number of further advantages. Because the entire interior of the cylindrical container is occupied by parallel gas passages and collecting plates differing in height in accordance with the vertical chords of the circular cross section, dead spaces are avoided in which explosive gas mixtures could form, e.g., when dust is collected from a converter. The scrapers which are pivoted on the axis of the housing move the dust in a simple manner into a dust discharge opening which extends throughout the length of the cylinder.

THE DRAWINGS FIG. 1 shows the pressure housing with the electric fields, collecting electrodes, charging electrodes and cleaning device.

FIG. 2 is a vertical sectional view taken on line II of FIG. 1.

FIGS. 3 and 4 are two enlarged sections taken through the cleaning device at right angles to each other.

FIGS. 5 and 6 are two enlarged sectional views taken at right angles to each other through a further embodiment of the cleaning device.

FIGS. 7, 8 and 9 show further details of the dust discharge device.

DESCRIPTION Cylindrical pressure container 1 having spherical end portions 2 and 2 contains electrical collecting fields 3 which are defined by collecting electrodes 4 and charging electrodes 5 and which are so arranged that gas passages 6 ,(FIG. 2) are formed, which define parallel planes. Each collecting electrode and charging electrode is suspended at its top end. The collecting electrodes are suspended with the aid of carriers 7 from the annular carriers 8. The charging electrodes or charging frames are suspended by means of transverse carriers 9, which are held by rods 10, from insulators 11, which are disposed outside the housing 1 in protective boxes 12. To clean the electrode system, the same is rapped in the center in the longitudinal direction at 13 and 14 by the hammers 15 and 16. The rapping rods 13 are secured to the electrodes and spaced by sheet metal elements 17, which are carried by the gangways 18. The collected dust is moved by a pivoted scraper 19 through the opening 20 into a dust conveyor 21. The scraper consists of two arms 23, which are pivoted to an axle 22. Movable longitudinal flaps 24 are mounted at the ends of the arms. A stiflening center piece 25 in the form of an arc is provided to which driving gear segments 36 are secured. The electrostatic precipitator rests on feet 26.

The gas to be cleaned (see the black arrow in FIG. l) flows through the crude gas inlet 27 into the dust separator. Gas distributing members 28 provide for a substantially homogeneous distribution of gas throughout the crosssection of the dust collector.

The dust-laden gas flows through the electric fields 3 and leaves the precipitator through the pure gas outlet 29. Explosion vents are indicated at 30 and, e.g., assembly openings at 31.

The dust discharge means and the scraper arrangement are illustrated in FIGS. 3 to 9.

The conveyance of the collected dust to the discharge opening 20 is accomplished with the aid of scoops 24, which are rotatably mounted at the lower ends of the struts or limbs 23. The scoops 24 are rotatable towards the center of the precipitator. Their rotation in the other direction is limited by a stop 40. Each pair of opposite scoops scrapes over the bottom of a collecting field, which is defined by two adjacent annular carriers. Short scoops 24 are also provided at the gas inlet and outlet. All scoops 24 disposed in the plane of FIG. 1 are secured to a continuous tube 32, which is rotatably mounted on the arms 23.

The scraper operates as follows: The upper scoop 24a moves downwardly and encounters the deposited dust. The resistance presented by the dust and the shape of the scoop causes this scoop 24a to be forced against its stop. The scoop is now in operating position and during a rotation of the two arms 23 moves the dust into the discharge opening 20. The opposite scoop 24b travels upwardly at the same time and during this movement slides over the dust contacted by it because when moving in this direction the scoop 24b can rotate about the axis of the tube 32. In the upper end position of the scoop 24b, the latter is turned to its operating position by a cam follower roller 33 and a cam plate 34 to ensure that, e.g., the descending scoop will not slide over any caked-on dust.

The scraper is driven by a plurality of pinions 35 in mesh with gear segments 36, which are secured to the arcuate reinforceing member 25. These pinions are carried by a common shaft 37, which extends through the housing and is driven by a gearmotor 38.

The dust which has collected adjacent to the gas-distributing plates 28 and which is not carried along by the scoops is moved by vibrating plates 39 to the blades 24.

In a scraper as shown in FIGS. 3 and 4, the shift to the operating position is effected only by the stop 34 by means of the followerroller 33 and the opposite scoop 241) can move freely as it slides upwardly over the dust to the opposite stop 34. FIGS. 5 and 6 shown an arrangement in which the push rod 41 ensures a positive control of the two opposite scoops so that one of them is in operating position at any given time.

FIGS. 5- to 9 shown a scraper which has postively controlled scoops. The upper scoop 24a moves downwardly to push the dust to the discharge opening 20. It is held in operating position by a spring element 42, into which the cam follower holder 43 has snapped. The opposite scoop 24b is lifted from the presure container 1 by a push rod 41 and moves upwardly. In its upper end position, the scoop is forced by the cam' follower roller 33 and the cam plate 34 against the stop 40, which is secured to the laminated plate 44. At the same time, the scoop is held in this operating position by the spring element 42, which has snapped onto the follower roller holder 43.

The opposite scoop is released from its locking means 42, 43 by the push rod 41 and is lifted from the pressure container by the push rod 41. At the same time, the dust which has been moved to the discharged opening 20 is thrown into the same.

We claim:

1. In an electrostatic precipitator for collecting dust,

which comprises a horizontal cylindrical pressure housing having a gas inlet at one end, a gas outlet at the other and a dust discharge opening in the bottom portion, plate-like collecting electrodes extending therethrough and defining parallel gas passages adapted to provide a horizontal gas flow path from said inlet to said outlet, and charging electrodes between said collecting electrodes, and cleaning means in the lower portion of said housing for removing the collected dust from the walls thereof to said dust discharge opening; the improvement comprising suspending said collecting electrodes from horizontal carriers which extend at the upper portion of the periphery of said housing and parallel to the center line thereof of the height of said collecting electrodes corresponding to the respective vertical chords of the circular cross-section of said housing.

2. The precipitator of claim 1, wherein a plurality of annular carriers are provided in said housing and are adapted to take up the weight of the internal fixtures and to stabilize said housing.

3. The precipitator of claim 1, wherein said dust discharge opening is provided on the underside of the housing and extends throughout the length thereof.

4. The precipitator of claim 3, wherein said cleaning means for removing the dust in the lower semicylindrical portion of the horizontal housing is removed by scrapers which are adapted for motion about the axis of said housing, extend throughout the length of the dust collector and are adapted to convey dust to said dust discharge opening.

5. The precipitator of claim 4, wherein said scrapers comprise two struts which extend at an angle of about 60 to each other, and scoops pivotedly mounted to the lower end of said struts.

6. The precipitator of claim 5, wherein said scoops are rotatable at their point of mounting on said struts toward the center of the dust collector and their rotation in the opposite direction is limited by a stop.

7. The precipitator of claim 6, wherein said scoops are mechanical positively positioned with respect to their direction of movement.

References Cited UNITED STATES PATENTS 1,981,455 11/1934 Knight 55-112 2,705,221 3/1955 Clark et al. 204306 2,964,126 12/1960 Peterson 55-430X 3,181,285 5/1965 Tepolt et al. 55145X 3,221,475 12/1965 Wiemer 55-122X FOREIGN PATENTS 553,908 3/1958 Canada 55-128 503,130 7/1930 Germany 55-112 565,152 10/1933 Germany 55112 717,705 11/1954 Great Britain 55-102 959,655 6/1964 Great Britain 55-101 DENNIS E. TALBERT, 111., Primary Examiner US. Cl. X.R. 

